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Registered Member #3429
Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288
radhoo wrote ...
@Xray: actually there is an easy way around that, probably you've all seen self-powered little radios using just a few components. would love to see your project, but since it was long ago, you probably don't have any pics.
Yeah, that was a loooooooooooooooooooooooong time ago, indeed! Sorry...
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
radhoo wrote ...
Thanks for the feedback, guys, I was about to think you're all away on some exotic holidays, drinking cocktails and having fun
I have been swamped with work of late and not off on holiday, though I still manage to drink a few cocktails and have fun
wrote ... @haxor5354: all electromagnetic waves (radio, light, X-rays, etc.) obey the inverse-square law. so yes, distance can be a problem.
This is operating with near field magnetic coupling rather than radiation I believe so you're actually worse off, the magnetic field from a current loop tends to decay with 1/r^3 rather than 1/r^2. Maybe take some readings of voltage on your load at measured distances, though I'd use a high power resistor rather than the lamp as the resistance of an incandescent bulb can change dramatically as it heats up and cools down.
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701
Mattski wrote ...
This is operating with near field magnetic coupling rather than radiation I believe so you're actually worse off, the magnetic field from a current loop tends to decay with 1/r^3 rather than 1/r^2. Maybe take some readings of voltage on your load at measured distances, though I'd use a high power resistor rather than the lamp as the resistance of an incandescent bulb can change dramatically as it heats up and cools down.
A very good suggestion, so I will do this as soon as I get the next time slot for this experiment. Too many things to do, too little time.
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
Increase the number of primary turns. It decreases current draw from what I've seen. I've gotten draw as low as 1 amp with around 5 + 5 turns on my mini ZVS wireless transmitter.... I assume if you add even more you'd get even lower draw. You'd have to experiment though!
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701
Yes, that will probably work, but I am open to other designs as well, as the royer oscillator might not function properly for lower voltages, unless I change the mosfets for BJTs.
On the other hand I need to go down scale, so the diameter of the coil needs to be reduced as well.
From what I understand, the diameter of the coil has a DIRECT impact on the transmission distance. How to overcome that? Any ideas?
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
I think you'd have to use some chip to generate "negative" resistance if you're using a royer at lower voltages... something like what's on page 14 on here;
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Wireless power transmitter
